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Understanding Newborn Characteristics and Development

The Newborn's Growth Patterns and Teething

The first upper and lower molars typically appear when the baby is between 13 and 19 months old.
The first upper and lower molars typically appear when the baby is between 13 and 19 months old.
©2006 Publications International, Ltd.

A baby's growth and development begin inside the womb. In fact, her most rapid rate of growth occurs during the first four months of the pregnancy. After birth, she continues to grow rapidly. Each baby's pattern of growing and developing is unique, influenced by gestational age at birth, birth size, body type, general state of health, quality of diet and exercise, and the sizes and growth patterns of the parents. On this page, we'll explain the growth patterns of a newborn, including their birth height and birth weight and how quickly they may grow during the first two years. In addition, you'll find information on newborn teething: when baby's teeth erupt and how to soothe the irritation that tooth formation often causes.

Birth Size

After spending approximately 40 weeks inside the womb, the average newborn weighs 7 1/2 pounds. Most babies weigh between 5 1/2 and 10 pounds. The average length of a newborn is 20 inches (50 centimeters), with a range of 18 to 22 inches. The average head circumference (the distance around the head) is 14 inches (35 centimeters).


At each visit, your doctor charts your child's growth. The best indicators of growth are weight, height, and head circumference. Plotting these growth measurements is a simple and extremely useful way of monitoring your child's state of health.

Rate of Growth

During the first few days after birth, you can expect your baby to lose 6 to 10 percent of her birth weight. Most of the weight lost is in the form of extra body water. If you are a mother who plans to breast-feed, your milk comes in during this time. The first milk, or colostrum, albeit scanty, is high in protein and sustains the baby as your milk supply increases.

After three to four days, the baby begins to regain weight and should attain or surpass her birth weight by 10 to 14 days. For the next three months, your infant grows at the astonishing rate of approximately an ounce a day. Between three and six months, her weight gain declines to four to five ounces a week. Between 6 and 12 months, the weight gain slows to two to three ounces a week. After the first year, the growth rate further tapers. During the second year of life, appetite sometimes diminishes as physical activity increases, resulting in temporary plateaus in growth.

If you have an average-size baby, you can expect her to double her birth weight by five months of age, triple it by one year, and quadruple it by two years. The average gain in length or height is 10 to 12 inches in the first year and 5 inches in the second year. Keep in mind that these predictions are estimates for the average-size baby. If your baby was smaller at birth, she may grow faster; if she was larger, she will probably grow at a slower rate.

The growth curve isn't always smooth. Babies often grow in spurts. If your baby is ill or preoccupied with acquiring a new physical skill, her growth rate may temporarily decline (she may be burning more calories and may be less interested in eating). Also bear in mind that bigger is not necessarily better. Obesity at any age should be avoided.

Tooth Formation and Eruption

Formation. Tooth buds for your baby's first teeth begin to form at about six weeks of fetal life. Between the fourth and fifth months of fetal life, some tooth buds become evident. By about the seventh month of fetal life, the tooth buds for all of your baby's primary (deciduous) teeth are formed. At birth, the crowns -- the portions of the teeth visible above the gums -- of your baby's front teeth are already formed and contain most of their enamel covering. The crowns for some of the other primary teeth are partially formed, and the tooth buds for some of the permanent molars are forming. By the time your child is three years old, the crowns of some permanent teeth are fairly well formed, and the tooth buds for the last molars have formed.

Teething. As early as three months of age, your baby may begin teething. Teething is marked by drooling, fretting, and chewing on just about anything in an attempt to reduce the discomfort of sore, swollen gums. Some babies exhibit these symptoms for up to four months before the first tooth finally erupts. If your baby seems uncomfortable, you can help reduce the pain and swelling in his gums by giving him firm, smooth, cool, unbreakable objects to chew. Massaging the inflamed gums with a clean fingertip may also help. Medications to numb painful gums are also available.

Don't be alarmed if your baby seems less interested in the breast or the bottle while teething; sucking increases the blood flow and hence the swelling and pain of the gums. If he's old enough, you might try offering him fluids from a cup.

Baby's first tooth.

Your baby's first tooth should appear when he is four to eight months old. However, it is not unusual for a child to be ten or more months old before the first tooth appears, and occasionally a baby is born with one or more teeth already erupted. Although most babies cut six to eight teeth by their first birthday, some normal babies have just two teeth or fewer. If your baby is approaching the age of one year and no teeth are evident (you may see the outlines of teeth before they erupt), you should talk to your baby's doctor about having a dental evaluation.

Baby teeth and chewing.

Even though all of your baby's teeth may have erupted by the time he is 1 1/2 to 2 years of age, you must exercise care in the foods you give him. A child's chewing ability usually is not fully developed until about the age of four years. Do not give children younger than this such foods as popcorn, nuts (especially peanuts), raw vegetables such as carrots, whole grapes, hot dogs, and round candies. If these and similar food items are not properly chewed, they may lodge in a small child's windpipe and cut off the air supply.

Teething and nutrition. Because a baby's teeth begin to form so early in fetal life, what the mother ate, or did not eat, during pregnancy can affect the development of the baby's teeth. However, a well-balanced diet can easily supply the nutritional needs of the teeth and their supporting bones and muscles; an ample supply of calcium is essential. After birth, the diet your baby's doctor recommends will contain the proper nutrients for your baby's healthy growth and development, including healthy tooth formation.

As your baby grows and cuts his first teeth, he begins to develop both gross motor and fine motor skills. You'll find a thorough exploration of your baby's first year of physical development on the following pages.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.